Skyrim's definitely got a lack of variety when it comes to voice actors. It hides that lack a bit better than in Oblivion, I'd say, since I haven't run into a situation yet where I'd find someone talking to themselves. It's a bit harder to notice because of another difference from Oblivion: ALL NPC conversations in Skyrim are scripted between specific individuals rather than randomly stopping to have a random chat with a random other NPC they happen to pass. In Skyrim, if they do not have a specific interaction scripted with another NPC, those other NPCs exist only as things to walk through or around.